Why No Nails, Screws or Power Tools?
A butsudan should be handmade of solid wood, free from metal fasteners, toxic glues and stains. It must be as near as possible to the tree from which the wood came. A shrine is, in my opinion, a reflection of the human body.
My butsudans are designed to be interacted with, caressed, tuned, nurtured. Such care can only bring one closer to what lies inside.
Besides, who wants to be stuck with a nail? Who wants their pores clogged with nasty, stinky stain? Who wants to be screamed at by a table saw?